ASTM A519 covers seamless mechanical tubing in carbon and alloy steels, and it is the specification most buyers quote when they ask for chromoly steel tubing or 4130 tubing. The tube is made without a weld, so the wall is uniform all round and there is no seam to open up when the part is machined, bored or threaded.
We draw A519 tube from 4 mm to 80 mm outside diameter in carbon grades and in chrome-moly grades, cold drawn, annealed, normalised or stress relieved. Every quotation is confirmed against the raw material price at the time of order, because steel does not hold a price for months.
Specifications
- Standard: ASTM A519 seamless carbon and alloy steel mechanical tubing
- Steel grade: 1010, 1018, 1020, 1026, 4130, 4140
- Size range: outside diameter 4-80 mm, wall 0.6-10 mm, or quoted to drawing
- Delivery condition: cold drawn, cold drawn and stress relieved, annealed, normalised
- Length: random 4-7 m, fixed length or cut to size on request
- Tolerance: commercial wall tolerance +-10 percent, closer on request; OD to the A519 tables
- Testing: chemical composition, tensile and yield, elongation, flattening, hardness, dimensions; NDT on request
- Documentation: EN 10204 3.1 mill test certificate, and 3.2 on request
Steel grades we draw
| Grade | Type | Nearest equivalent | Typical use |
|---|---|---|---|
| 1010 | Carbon | 10#, S10C | Bushings, low-stress machined parts, tube that will be formed |
| 1018 | Carbon | 18#, S18C | Shafts, pins, parts that need a better machined finish |
| 1020 | Carbon | 20#, S20C | The workhorse grade: general machined components, spacers, sleeves |
| 1026 | Carbon | 25Mn, S25C | Higher-strength mechanical parts without heat treatment |
| 4130 | Chromoly | 25CrMo4, 1.7218 | Strength at lower weight: forks, frames, shafts, airframe and motorsport parts |
| 4140 | Chromoly | 42CrMo4, 1.7225 | Parts that are hardened and tempered after machining |
1020 covers most mechanical work, and it is the grade we hold in the widest size range. 4130 and 4140 are the alloy side of the same specification, supplied against order, and they are the grades that customers describe as chromoly steel tube rather than by the A519 number.
Chromoly, chrome-moly, 4130: three names, one tube
Almost nobody orders this material by its standard number. The same seamless tube is written six different ways depending on who is buying it, and a page that only says “ASTM A519” leaves most of them behind.
| Name in the enquiry | Who writes it | What it means |
|---|---|---|
| chromoly steel tubing / chromoly tubing | US job shops, motorsport, chassis builders | Seamless 4130 or 4140 tube |
| 4130 chromoly steel tubing / 4130 steel tubing | Buyers who already know the grade | Same tube, grade fixed at 4130 |
| 4130 chromoly pipe | Airframe, bicycle, oil tool shops | Same mill product, sized and sold as pipe |
| 4130 chrome moly tubing | Older US drawings and catalogues | Chrome-moly is the long form of chromoly |
| CDS / cold drawn seamless | UK and European buyers | A519 equivalent in the cold drawn condition |
| 25CrMo4 | German and European drawings | European designation for 4130 |
4130 carries roughly 0.30 percent carbon with 0.80-1.10 percent chromium and 0.15-0.25 percent molybdenum, which lifts hardenability and fatigue strength well above 1020 without making the tube difficult to machine. That is the reason a fork leg, a frame node or a drive shaft can be made thinner and lighter in 4130 than in a plain carbon grade. When a drawing says 4130 chrome moly tubing and also quotes a wall tolerance, both the grade and the A519 tolerance class have to be confirmed before the tube is drawn.
Seamless, DOM or ERW: which route for which part
| Route | How it is made | Seam | Wall and bore | Best for |
|---|---|---|---|---|
| A519 seamless | Billet pierced and cold drawn | None | Uniform wall, no seam to machine through | Pressure parts, thin walls, parts bored or threaded after cutting |
| A513 Type 5 DOM | ERW tube drawn over a mandrel | Weld flash removed | Very concentric, clean bore | Shock bodies, rollers, bushings, high-volume parts |
| A513 Type 1 ERW | Strip formed and welded | Visible weld | Wall variation follows the strip | Low-pressure lines, furniture, general fabrication |
For chromoly the choice is usually decided by the wall: below about 1.5 mm, or wherever the bore is machined after cutting, seamless is the safer route. Where the part is a plain tube with a bore that only needs to be round, DOM does the same job at a lower price.
Sizes and tolerances
The table below lists the sizes that move most often. Sizes outside it are drawn to order rather than cut from stock, so lead time is longer but the size is not a problem.
| Outside diameter | Inch equivalent | Wall range | Note |
|---|---|---|---|
| 12 mm | 0.472 in | 1.0-2.0 mm | Small machined parts, pins |
| 16 mm | 0.630 in | 1.0-3.0 mm | Sleeves, spacers |
| 20 mm | 0.787 in | 1.0-4.0 mm | General mechanical tube |
| 25.4 mm | 1 in | 1.2-4.0 mm | Inch drawings |
| 31.75 mm | 1-1/4 in | 1.5-5.0 mm | Bushings, rollers |
| 38.1 mm | 1-1/2 in | 1.5-6.0 mm | Shock bodies |
| 41.3 mm | 1-5/8 in | 2.1 mm (0.083 in) | 1-5/8 chromoly tubing, thin-wall structural parts |
| 50.8 mm | 2 in | 2.0-8.0 mm | Larger mechanical parts |
| 63.5 mm | 2-1/2 in | 2.5-10.0 mm | Heavy-section work |
Straightness is checked on the bench, and tube can be supplied cut to length with deburred ends so that it goes straight into the machine. If the drawing gives an ID and a wall rather than an OD, send the ID: the draw schedule is set from the bore whenever the bore is the working surface.
TIG welding 4130 chromoly tubing
4130 welds cleanly with TIG, which is why chassis and fork builders ask for it in the first place, but the condition of the tube matters more than the filler. Cold drawn tube carries residual stress from the draw, and welding it in that condition concentrates stress at the joint. Two rules avoid most of the trouble: weld in the annealed or normalised condition where the part is highly loaded, and use ER80S-D2 filler rather than a mild steel rod so that the weld matches the parent metal.
For walls above about 3 mm a preheat of 150-200 C is normal practice, followed by a slow cool and, on highly stressed parts, a stress relief after welding. Tubes ordered for welding are supplied normalised on request, with the heat number marked so that the certificate and the part can be traced back to the same lot.
Quality control and packing
Each lot is tested for chemical composition, yield and tensile strength, elongation, flattening and dimensions before it leaves the works, with visual inspection and NDT available on request. Tubes are protected with anti-rust oil, ends are capped, and bundles are strapped and packed seaworthy, in wooden cases where the size or the customer calls for it. Marking follows the purchase order, in English or in the customer’s language.
FAQ
What is ASTM A519 tubing used for?
It is mechanical tubing, so it is used for parts rather than for conveying fluid: shafts, spindles, bushings, rollers, hydraulic components, and structural parts in motorcycles and motorsport where a seamless wall matters.
Is A519 the same as 4130?
No. A519 is the specification; 4130 is one of the grades inside it. A tube can be A519 in 1020 and contain no chromium at all, which is why the grade has to be written on the order as well as the standard.
What is chromoly steel tubing?
Chromoly is the workshop name for chrome-molybdenum steel, and in tube it almost always means 4130 or 4140. When a customer asks for chromoly tubing they normally mean seamless A519 tube in 4130, drawn to a wall that suits the part.
Is 4130 chromoly pipe the same as 4130 tubing?
The mill product is the same. Pipe is sized and sold by nominal bore for flow, tube by outside diameter and wall for structure, so a 4130 chromoly pipe order usually comes with a wall and an OD on the drawing instead of a schedule number.
Can you TIG weld 4130 chromoly tubing?
Yes. Use ER80S-D2 filler, preheat above roughly 3 mm wall, cool slowly, and stress relieve highly loaded parts. Ordering the tube in the normalised condition removes most of the residual stress before the weld is made.
Do you supply 1-5/8 inch chromoly tubing?
Yes, 41.3 mm OD is a size we draw, with 0.083 in wall as the common thin-wall combination. Other inch sizes are drawn to order, so a list of OD and wall is enough to quote.
What is the difference between A519 and A513?
A513 is welded mechanical tubing, including DOM; A519 is seamless. Both are mechanical tubing specifications, so the choice between them is a choice between a seam and no seam, and it shows up in both the price and the wall tolerance.
Are you a chromoly tubing supplier outside the US?
We export from China to Europe, Russia, Turkey, Southeast Asia and South America, with EN 10204 3.1 certificates and packing to the destination port. Chromoly tubing suppliers are usually asked for a heat number and a wall tolerance before anything else, and both are on our quotation.
Related pages
- Seamless steel tube: all standards and sizes
- DOM tubing, ASTM A513 Type 5
- DIN 2391 seamless precision tube
- ASTM A519 standard page: grades and tolerances
Request a quotation: send your size list or drawing through our contact page. We reply within one working day with price, tolerance and lead time.